The objectives of this research program are to increase our understanding of the morphologic and functional features of normal and abnormal human corneal endothelium and to develop a method for long-term corneal preservation. Because of biologic differences between species, human eyes will be studied whenever possible. Clinical specular microscopy and ocular anterior segment fluorophotometry will be used to study corneal endothelial abnormalities in two groups of patients. First, patients with long- standing Type I diabetes mellitus will be examined for abnormalities in endothelial function; diabetic corneal endothelial cells have been shown previously to have morphologic abnormalities that respond to treatment. Second, the influence of sensory innervation upon corneal hydration in cold ambient air will be investigated in patients with unilateral, surgically- induced corneal anesthesia. Endothelial cell survival after corneal transplantation will be test in patients receiving corneas preserved by new short-term methods. Specular microscopy will be performed preoperatively and at intervals for ten years postoperatively to monitor chronic endothelial survival and morphologic changes in 862 patients who have undergone cataract extraction and 500 patients who have undergone corneal transplantation. Finally, a new method of permanent corneal storage at low temperatures by vitrification will be developed for human corneas and tested by keratoplasty, first in cats and then in humans. Such a method will facilitate the distribution of donor corneas, allow matching of tissue types if necessary, and increase the supply of suitable donor corneas by preventing their loss for logistical reasons.